Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F4/00—Polymerisation catalysts
  • C08F4/06—Metallic compounds other than hydrides and other than metallo-organic compounds; Boron halide or aluminium halide complexes with organic compounds containing oxygen
  • C08F4/22—Metallic compounds other than hydrides and other than metallo-organic compounds; Boron halide or aluminium halide complexes with organic compounds containing oxygen of chromium, molybdenum or tungsten
  • C08F4/24—Oxides
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F10/00—Homopolymers and copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
  • C08F10/02—Ethene
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J23/24—Chromium, molybdenum or tungsten
  • B01J23/26—Chromium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/0201—Impregnation
  • B01J37/0203—Impregnation the impregnation liquid containing organic compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F210/00—Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
  • C08F210/16—Copolymers of ethene with alpha-alkenes, e.g. EP rubbers

Definitions

• the invention relates to a process for producing supported chromium catalysts for the polymerization of olefins and to the catalysts which can be obtained by the process according to the invention
• supported chromium catalysts refer to chromium catalysts as used for the polymerization of ⁇ -olefins (cf. M P McDaniel, Adv Cat 33, pages 47 to 98 (1985))
• HD-PE high-density polyethylene
• the conditions in the manufacture of the supports and the catalysts determine the chemical composition, pore structure, particle size and shape of the catalysts.
• the catalysts are activated at high temperatures under oxidizing conditions in order to stabilize chromium on the catalyst surface. Then the catalyst reduced by adding ethene or additional reducing agents to form the catalytically active species that catalyzes the polymerization
• Suitable carriers can be produced according to DE-A 25 40 279. This process relates to the production of a hydrogel of silica containing 10 to 25% by weight of solids (calculated as SiO 2 ), the particles of which are largely spherical.
• the silicon-aluminum-phosphate carriers known from DE-A 42 28 883 can be used
• the chromium oxide catalysts are generally prepared in accordance with DE-A 25 40 279 or in a similar manner.
• the xerogel obtained is dissolved in a 0.05 to 15% strength by weight solution of a chromium compound which under the reaction conditions mentioned below essentially changes into a chromium (VI) compound, in an alcohol which contains a maximum of 20% by weight of water, by evaporating the alcohol, the desired amount of chromium is loaded and the resulting product in an anhydrous gas stream which Contains at least 10 vol% oxygen, heated to temperatures in the range from 300 to 1100 ° C over a period of 10 to 1000 min
• the known supported chromium catalysts have a number of disadvantages. It has been shown that the chromium compound attaches above all to the outer regions of the catalyst carrier, while the inner regions are wetted to a much lesser extent, since the inner regions of the catalyst particles also adhere to the Such an inhomogeneous chromium distribution is highly undesirable. In addition, chromium agglomerates are frequently observed, which result from the localized deposition of the chromium compounds on the catalyst surface
• the solution of the task according to the invention is based on a process for producing supported chromium catalysts by loading a xerogel carrier with chromium a) adding a volume of a 0.025 to 15% by weight solution of a chromium compound or a volume of a solution containing 0.025 to 7.8% by weight of Cr to the xerogel carrier, which when heated under oxidizing conditions to temperatures in the Range from 300 to 1100 ° C over a period of 10 to 1000 min essentially changes into a chromium (VI) compound, in a solvent containing a maximum of 20% by weight of water, and then
• Xerogels are gels that have lost their liquid in some way (by evaporation, squeezing or suction), whereby the spatial arrangement of the network changes, so that the distances between the structural elements only have dimensions of atomic distances.
• Xerogel carriers can be placed on silica gel -Based according to DE-A 25 40 279
• silica gel-based xerogel carriers there are also xerogel carriers based on aluminum phosphate or xerogel carriers based on aluminum oxide-silicon oxide cogel or aluminum silicate -Gels in question (cf. US-A 2 825 721 or US-A 2 930 789)
• those with a large pore volume of up to 3 ml / g are preferred
• Suitable solvents for the chromium compound are alcohols or C 3 -C 5 -alkanones.
• C 1 -C 4 -alcohols are preferred, in particular methanol
• Suitable chromium compounds are, for example, chromium trioxide, chromium hydroxide and soluble salts of trivalent chromium with an organic or inorganic acid such as acetate, oxalate, sulfate or nitrate Salts of such acids are used with particular preference which, when activated, essentially change into chromium (VI) without residues, such as chromium (III) nitrate nona hydrate.
• the volume of a solvent containing the chromium compound is added to the xerogel carrier. The volume this chromium solution is smaller than the pore volume of the xerogel carrier
• the pore volume of the xerogel carrier is determined by the method described in the exemplary embodiment (see Table 1).
• the volume of the solvent is preferably less than 95%, especially less than 90%, in particular 75 to 85%, of the pore volume of the xerogel. carrier
• the xerogel carrier and the chromium solution are then mixed, for example, in a double-cone mixer.
• the solvent and, if appropriate, the water contained therein are mixed at temperatures in the range from 20 to 200 ° C., preferably from 100 to 150 ° C, and pressures in the range from 1.3 mbar to 1 bar, preferably from 300 to 900 mbar
• the catalyst is activated (optionally with the addition of fluorinating agents such as ASF, ammonium hexafluorosilicate) under oxidizing conditions, for example in a water-free gas stream which contains at least 10% by volume oxygen, preferably at temperatures in the range from 300 to 1100 ° C. particularly preferably at temperatures from 500 to 800 ° C., for a period of preferably 60 to 1000 min, particularly preferably from 200 to 800 min, for example in a fluidized bed through which air flows
• fluorinating agents such as ASF, ammonium hexafluorosilicate
• the process according to the invention leads to a catalyst with a chromium content of 0.1 to 3% by weight, preferably 0.7 to 1.5% by weight, particularly preferably 0.9 to 1.2% by weight.
• a catalyst with a chromium content of 0.1 to 3% by weight, preferably 0.7 to 1.5% by weight, particularly preferably 0.9 to 1.2% by weight.
• Preferred unsaturated compounds are ethene or C 3 - to Cs- ⁇ -monoolefins
• xerogel carriers based on silica gel were impregnated with solutions of a chromium compound in acetic acid, the volume of which corresponded to the pore volume of the carrier (US Pat. No. 4,967,029 and WO 95/18782)
• this catalyst can be used for the polymerization of ethene and / or of C 3 -C -o- ⁇ -monoolefins. Because of the improved production process, the catalyst according to the invention has a increased productivity and leads to polymers with improved mechanical properties, for example increased stress crack resistance
• Another object of the invention is a process for the polymerization of ethene and / or of C 3 -C -o- ⁇ -monoolefins, in which a supported chromium catalyst according to the invention is used as a catalyst
• Another subject is polyethylenes which can be obtained by the aforementioned process
• the resulting product was heated to a temperature of 630 ° C. in a fluidized bed, through which air flowed, and then removed again. cool From 140 ° C, the fluidized bed was flushed with nitrogen in order to remove traces of oxygen (which interfere with the polymerization)
• the catalyst according to the invention and the comparative catalyst were used for the polymerization of ethene and hexene in a 0.2 m 3 loop reactor.
• the melt flow rate and the density were adjusted via the reactor temperature and the comonomer concentration in the suspension medium.
• Isobutane was used as the suspension medium.
• the internal reactor pressure was 39 bar, the Reactor density was approx. 640 kg / m 3.
• the polymerization was carried out continuously while maintaining the ethylene partial pressure. The data are summarized in the tables below
• the pore volume was determined as follows. 5 g of the substance to be tested were weighed into a dry powder bottle (150 ml) with a screw cap. Distilled water was added in portions from a burette (initially 2 ml, later less and less) The screw cap was closed and the contents were mixed by vigorous rubbing. Then the bottle was placed on a cork board with a powerful blow and then turned over.If about 1/3 of the sample remains on the bottom of the bottle, the pores are saturated g of the sample converted The standard deviation of the pore volume measurement is ⁇ 0.02 ml / g
• the catalyst grains are embedded in a non-polar resin and cut with the aid of a milling cutter.
• the resin component must be designed so that it does not react with the active components.
• a roughly 30 nm thick layer is cut on the prepared section Amorphous carbon layer applied by vapor deposition
• the element distribution in the grain is shown with the help of energy-dispersive X-ray analysis.
• the electrons striking the solid body excite characteristic X-rays at a depth of 2 to 3 ⁇ m below the point of impact by impact ionization
• the electron beam is guided over the surface in a 256 x 256 point grid.
• An automatic sample table guide can be used a large number of catalyst grains are measured.
• the maximum lateral resolution for the element distribution is 1 ⁇ m.
• the chromium content is determined in the middle of the grain cross-section and immediately below the grain surface and is given in arbitrary units (wU) Table 2
• the catalyst according to the invention has a more uniform chromium distribution than the comparative catalyst (chromium, outside / chromium, inside 3.8 versus 6.7, see Table 1), with comparable density and comparable flow behavior the catalyst according to the invention has a productivity increase of almost 20% compared to the comparative catalyst and the polymer produced with the catalyst according to the invention has an improved stress crack resistance

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Engineering & Computer Science (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Health & Medical Sciences (AREA)
• Polymerization Catalysts (AREA)
• Transition And Organic Metals Composition Catalysts For Addition Polymerization (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Catalysts (AREA)

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• 1999
  • 1999-09-09 DE DE19943167A patent/DE19943167A1/de not_active Withdrawn
• 2000
  • 2000-08-31 EP EP00967636A patent/EP1210176B1/fr not_active Expired - Lifetime
  • 2000-08-31 ES ES00967636T patent/ES2239045T3/es not_active Expired - Lifetime
  • 2000-08-31 KR KR1020027003106A patent/KR100727278B1/ko not_active IP Right Cessation
  • 2000-08-31 WO PCT/EP2000/008484 patent/WO2001017675A1/fr active IP Right Grant
  • 2000-08-31 DE DE50009811T patent/DE50009811D1/de not_active Expired - Lifetime
  • 2000-08-31 JP JP2001521457A patent/JP2003508593A/ja active Pending
  • 2000-08-31 AT AT00967636T patent/ATE290926T1/de not_active IP Right Cessation
  • 2000-08-31 US US10/070,341 patent/US6608151B1/en not_active Expired - Lifetime
  • 2000-08-31 AU AU77742/00A patent/AU7774200A/en not_active Abandoned
  • 2000-08-31 CN CNB008126240A patent/CN1200765C/zh not_active Expired - Fee Related

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